/* "Species" - a CoreWars evolver.  Copyright (C) 2003 'Varfar' 
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 1, or (at your option) any later
 * version. 
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details. 
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 675 Mass Ave, Cambridge, MA 02139, USA. 
 */

#include "species.hpp"
#include "inst_gen_weighted_random.hpp"
#include "rand.hpp"
#include "opcode_branch_lookup.hpp"
using namespace std;

/***** CInstGeneratorWeightedRandom class implementation *********************/

CInstGeneratorWeightedRandom::CInstGeneratorWeightedRandom() {
	_type = WEIGHTED_RANDOM; // very important line!
	// init the freq_hint table to default values
	_freq_hint_sum = 0.0F;
	for(int i=0; i<OPCODE_LAST; ++i) {
		_freq_hint[(OPCODE)i] = OPCODE_FREQ_HINT_DEFAULT;
		_freq_hint_sum += _freq_hint[(OPCODE)i];
	}
	_branch_bias = false;
	_branch_pivot = BRANCH_PIVOT_DEFAULT;
}

float CInstGeneratorWeightedRandom::get_freq_hint(const OPCODE opcode) {
	if(!(0 <= opcode < OPCODE_LAST))
		PANIC(BAD_OPCODE,"request for invalid opcode in freq_hint",NULL);
	return _freq_hint[opcode];
}

void CInstGeneratorWeightedRandom::set_freq_hint(const OPCODE opcode,const float val) {
	if(!(0 <= opcode < OPCODE_LAST))
		PANIC(BAD_OPCODE,"attempt to set invalid opcode in freq_hint",NULL);
	if(0.0F > val)
		PANIC(NEG_OPCODEFREQ_HINT,"attempt to set negative freq_hint",NULL);
	_freq_hint_sum -= _freq_hint[opcode];
	_freq_hint[opcode] = val;
	_freq_hint_sum += _freq_hint[opcode];
	if(0.0F == _freq_hint_sum)
		PANIC(ZERO_OPCODEFREQ_HINT_SUM,"total freq_hints have zero sum",NULL);
}

void CInstGeneratorWeightedRandom::suggest_instruction(insn_t &instruction,const MODE /*mode*/) {
	// NOTE: might be more fair to maintain a _branch_hint_sum and scale the roulette to a single pass
	
	// generate a random number between 0.0F and freq_hint_sum
	const float x = CRand::frand(_freq_hint_sum); // the target value
	float y = 0.0F, // an iterator through all buckets
		bucket, // an intermediary for weighing branch instructions
		branch_weight = 1.0F; // a scale relative to the pivot
	int i;
	// need to weigh branches?
	if(_branch_bias) {
		// seek back to find a branch
		for(i=index()-1; i>0; --i) {
			if(OPCODE_IS_BRANCH[chromosome()->code(i).opcode()]) { // found?
				// calculate weight based on distance to pivot
				branch_weight = ((index()-i) / _branch_pivot);
				break; // stop searching then
			}
		}
	}
	// rolette-wheel to the choosen instruction
	do {
		for(i=0; i<OPCODE_LAST; ++i) {
			bucket = _freq_hint[(OPCODE)i];
			if(_branch_bias && OPCODE_IS_BRANCH[(OPCODE)i]) {
				bucket *= branch_weight;
			}
			y += bucket;
			if(y > x) { // found?
				generate_completely_random(instruction);
				instruction.set_opcode((OPCODE)i);
				return;
			}
		}
		if(!_branch_bias)
			cerr << "WARNING: roulette past end of freq_hint range" << endl;
	} while(true);
}

void CInstGeneratorWeightedRandom::read_ini_impl(INIFile &ini) {
	// load the freq_hints
	int i;
	KeyValuePair *kvp;
	// opcodes
	for(i=0; i<OPCODE_LAST; ++i) {
		// get it
		kvp = ini.get(MNEMONIC_OPCODE((OPCODE)i));
		if(0 == kvp) // not set?
			set_freq_hint((OPCODE)i,OPCODE_FREQ_HINT_DEFAULT);
		else
			set_freq_hint((OPCODE)i,kvp->getValueAsFloat(OPCODE_FREQ_HINT_DEFAULT));
	}
	// branch pivot?
	kvp = ini.get("branch_bias");
	if(0 != kvp) { // set
		_branch_bias = kvp->getValueAsBool(_branch_bias);
		if(_branch_bias) {
			kvp = ini.get("branch_pivot");
			if(0 != kvp) {
				_branch_pivot = kvp->getValueAsInt(_branch_pivot);
				if(1 > _branch_pivot) { // avoid a divzero further down the line!
					PANIC(NEG_OPCODEFREQ_HINT,"branch_pivot cannot be less than 1",NULL);
				}
			}
		}
	}
}

CInstGenerator *CInstGeneratorWeightedRandom::read_override_ini_impl(INIFile &ini) {
	CInstGeneratorWeightedRandom *ret = this;
	int i, pivot;
	bool bias;
	KeyValuePair *kvp;
	// load the freq_hints
	for(i=0; i<OPCODE_LAST; ++i) {
		// get it
		kvp = ini.get(MNEMONIC_OPCODE((OPCODE)i));
		if(0 != kvp) { // set?
			if(this == ret) { // first opccode to be overridden?
				ret = new CInstGeneratorWeightedRandom(*this); // create a copy
			}
			ret->set_freq_hint((OPCODE)i,kvp->getValueAsFloat(OPCODE_FREQ_HINT_DEFAULT));
		}
	}
	// bias?
	kvp = ini.get("branch_bias");
	if(0 != kvp) { // set?
		bias = kvp->getValueAsBool(ret->_branch_bias);
		if(bias != ret->_branch_bias) { // overriden?
			if(this == ret) { // first thing to be overriden?
				ret = new CInstGeneratorWeightedRandom(*this); // create a copy
			}
			ret->_branch_bias = bias;
		}
		kvp = ini.get("branch_pivot");
	}
	// pivot?  We'll ignore in the case when bias isn't set to keep things clean
	if(ret->_branch_bias) {
		kvp = ini.get("branch_pivot");
		if(0 != kvp) { // set?
			pivot = kvp->getValueAsInt(ret->_branch_pivot);
			if(1 > pivot) { // avoid a divzero further down the line!
				PANIC(NEG_OPCODEFREQ_HINT,"branch_pivot cannot be less than 1",NULL);
			}
			if(pivot != ret->_branch_pivot) {
				if(this == ret) { // first thing to be overriden?
					ret = new CInstGeneratorWeightedRandom(*this); // create a copy
				}
				ret->_branch_pivot = pivot;
			}
		}
	}
	// done
	return ret;
}

void CInstGeneratorWeightedRandom::write_ini(ostream &os) {
	int i;
	// list freq_hints
	for(i=0; i<OPCODE_LAST; ++i)
		if(OPCODE_FREQ_HINT_DEFAULT != _freq_hint[(OPCODE)i]) // not default value?
			os << MNEMONIC_OPCODE((OPCODE)i) << '=' << _freq_hint[(OPCODE)i] << endl;
	// list pivot stuff
	if(_branch_bias) {
		os << "branch_bias=" << _branch_bias << endl;
		if(BRANCH_PIVOT_DEFAULT != _branch_pivot) {
			os << "branch_pivot=" << _branch_pivot << endl;
		}
	}
}

void CInstGeneratorWeightedRandom::write_override_ini(ostream &os,const CInstGenerator *parent) {
	if(this == parent) // no override at all?
		return;
	if(same_type(parent,this)) { // not same concrete type?
		write_ini(os);
		return;
	}
	int i;
	// list freq_hints
	for(i=0; i<OPCODE_LAST; ++i)
		if(((CInstGeneratorWeightedRandom*)parent)->_freq_hint[(OPCODE)i] != _freq_hint[(OPCODE)i]) // overriden?
			os << MNEMONIC_OPCODE((OPCODE)i) << '=' << _freq_hint[(OPCODE)i] << endl;
	// branch pivot stuff
	if(_branch_bias != ((CInstGeneratorWeightedRandom*)parent)->_branch_bias) {
		os << "branch_bias=" << _branch_bias << endl;
	}
	if(_branch_bias && (_branch_pivot != ((CInstGeneratorWeightedRandom*)parent)->_branch_pivot)) {
		os << "branch_pivot=" << _branch_pivot << endl;
	}
}